Staging flattens a culture directory's .psd1 into the output root

[tablackburn]

Found while researching #207. Reading the code confirms it; it is also visible in that issue's own reproduction output.

What happens

Build-PSBuildModule stages the module's loose files with:

$getChildItemSplat = @{
    Path    = $Path
    Include = "*.psm1", "*.psd1", "*.ps1xml"
    Depth   = 1
}
Get-ChildItem @getChildItemSplat |
    Copy-Item -Destination $DestinationPath -Force

-Depth 1 implies recursion one level down, so this matches en-US/Messages.psd1 — and Copy-Item -Destination $DestinationPath writes it flat into the output root, discarding the directory it came from.

A module with a localized Messages.psd1 therefore builds an output containing a stray Messages.psd1 at the root that nothing reads. If CopyDirectories also names en-US, the correct copy is there too, and the built tree carries both.

Why it matters, mildly

Nothing breaks. Import-LocalizedData resolves through the culture directory and ignores the stray file, and a module without a culture directory never hits it. The costs are that the published package carries a file that serves no purpose and misleads anyone reading the tree, and that a consumer debugging localization finds two copies of the same file and has to work out which one is live.

It is also the same root cause as #210, seen from the other side: the depth-1 glob is trying to serve two purposes — collect the root manifest and module file, and leave everything else to CopyDirectories — and reaches one level too far.

Options

1. Drop -Depth 1, so the glob matches only the root. The manifest and root module are always at the root, so nothing intended is lost. Anything deeper is CopyDirectories' job. Smallest change.
2. Preserve relative paths when copying, so en-US/Messages.psd1 lands at en-US/Messages.psd1. More faithful, and it would partly address Compiling drops a hand-written about_<Module>.help.txt unless CopyDirectories names the culture directory #210 — but it makes the glob a second, implicit staging mechanism competing with CopyDirectories, which is how the two got tangled in the first place.
3. Leave it. The stray file is inert.

(1) looks right, and it is a one-word deletion. But -Depth 1 was presumably added deliberately at some point, and I could not find what for — worth a moment's thought before removing it, in case some layout depends on it.

Related: #206, #207 and #210 are all in this same staging logic. Worth deciding together.

[tablackburn]

Correction: option 1 in the description above is wrong and must not be implemented as written. I wrote it; it does not work.

Dropping -Depth 1 on its own returns an empty result set. Without recursion, -Include filters against the leaf of -Path rather than against the directory's children, so nothing matches. That would stage no manifest and no root module, and compile mode would then run Get-Content against a root module that does not exist.

Measured on PowerShell 7.6.5 against this repository's own PowerShellBuild/ source directory:

-Path	-Depth 1	Result
$Path	yes	en-US\Messages.psd1, PowerShellBuild.psd1, PowerShellBuild.psm1, ScriptAnalyzerSettings.psd1 -- the bug
$Path\*	yes	same four -- still wrong
$Path	no	(empty) -- breaks the build
$Path\*	no	the three root files only -- correct

So the fix requires both changes together: set Path to [IO.Path]::Combine($Path, '*') and remove Depth. Neither alone is sufficient, and one of them alone is actively harmful.

Two further findings that were not in the original description:

This is host-dependent. On Windows PowerShell 5.1, -Depth combined with -Include silently degrades to a full -Recurse, so files far below depth 1 are flattened into the output root. PowerShell 7 honours the depth. The contents of a published package therefore depend on which host built it, and same-named files at different depths can collide. -Depth without -Include behaves correctly on 5.1; it is the combination that breaks.

The -Depth 1 was not deliberate. git log -S traces it to two commits thirteen seconds apart in 2018. The second is the readme-discovery glob, where "project root plus one level down" is the genuine intent; the pattern was carried into the staging glob, where the adjacent CopyDirectories loop shows the intent is root loose files only. That answers the open question in the description.

Those readme globs still carry the same pattern today, at PowerShellBuild/psakeFile.ps1:94 and PowerShellBuild/IB.tasks.ps1:29, where on 5.1 they recurse the entire project root and Select-Object -First 1 then picks an arbitrary readme. Same root cause, worth folding into the same change.